“…In the theoretical model proposed by Rush and Driscoll (Rush & Driscoll, 1968), the head was modeled as three conducting concentric spherical shells consisting of the scalp, skull, and brain tissue. Each shell is considered as homogeneous with a dielectric property of the tissue it represents (Al-Mutawaly & Findlay, 1998; Deng, et al, 2013; Deng, Lisanby, & Peterchev, 2015; Deng, et al, 2008; Miranda, Lomarev, & Hallett, 2006; Ravazzani, Ruohonen, Grandori, & Tognola, 1996). With increasing computational power, progress in brain imaging, and available software tools, spherical head models were replaced by still idealized imaging-based head models (Fig.…”